Jig for orientation-blow molding piece

Abstract

A jig used for a blow-molding machine for fabricating a bottle-shaped container of biaxially oriented plastic, which comprises advantageously a core shaft elevationally movably inserted in a mandrel and having a blow-molding air passage for longitudinally orienting the piece, and a heat insulating layer provided on the outer periphery of the core shaft for heating the piece upon irradiation of heat rays such as far infrared rays to thereby externally heat the piece and also internally heat the piece. Thus, the piece is uniformly heated in or immediately before the blow-molding of the piece so as to improve the molding accuracy of the piece into a bottle-shaped container in the blow molding mold.

What is claimed is: 
     
       1. A device for heating an injection molded resin piece having a neck, prior to biaxial orientation blow molding, comprising: a rotary turntable;   a cover disposed above and spaced from said turntable;   a jig disposed at the periphery of said turntable, comprising: a neck support for holding the piece in neck portion downward position;   a mandrel disposed beneath said neck support;   an elevationally reciprocally movable core shaft inserted in said mandrel and extending through said neck support for longitudinally orienting the piece, having a blow-molding air-passage;   a heat-insulating layer coated on the outer periphery of said core shaft;   a plurality of infrared or far infrared ray heating elements disposed inside said cover in the vicinity of the periphery of the turntable, said insulating layer comprising material which will cause heating of the interior of the piece held by said jig due to heating of said insulating layer by special wavelength rays of said heating elements upon irradiation of said heating elements.     
     
     
       2. A device according to claim 1, further comprising a core guide made of refractory synthetic resin disposed in the neck support. 
     
     
       3. A device according to claim 1, wherein said neck support is disposed above a heat-insulating plate provided on the top of said mandrel, and said core shaft further comprises a core top made of heat-insulating material having an inverted taper shape or spherical shape for stopping the heat conduction to and from the piece and for preventing the piece from sticking onto the core shaft when it is subjected to the longitudinal orientation. 
     
     
       4. A device according to claim 1, wherein said core shaft is made of iron alloy, and said device further comprises a high frequency induction heater for heating said core shaft. 
     
     
       5. A device according to claim 1, wherein said heat-insulating layer is made of zirconium ceramic.